Study On Genotyping And Pathogenicity Of Borrelia Burgdorferi Sensu Lato Isolated From China

To investigate the distribution of Borrelia burgdorferi sensu lato genotypes in China, a survey was performed on Lyme disease spirochetes in 6 species ticks collected from Inner Mongolia, Heilongjiang, Jilin, Zhejiang, Shandong and Fujian provinces. Twenty-six isolates were obtained from Ixodes persulcatus ticks.All the 26 isolates were genotyped by restriction fragment length polymorphism (RFLP), single-strand conformation polymorphism (SSCP) and sequence analysis based on 5S-23S rRNA intergenic spacer. The gene mutations among the digested site of Mse I in 5S-23S rRNA intergenic spacer made it impossible to genetype the isolates accurately. Sequence analysis was the most feasible method of genotyping. By sequencing, a total of 36 strains obtained from China were genotyped as 3 genospecies: B. valaslana, B. afzelii and B. garinii. B. garinii was the dominant genospecies, and distributed in Inner Mongolia, Heilongjiang, and Jilin. B. afzelii just distributed in Heiongjiang, and B. valaslana in Yunnan. The distribution of the genospecies showed significant regional difference.To study the pathogenicity of B. garinii of China, three isolates of B. garinii were subcutaneously inoculated in BALB/c mice for 3 times. The mice were executed at 40^th and 87^th day after inoculation. Pathologic damages and the distribution of the antigen in the organs were respectively observed by HE stain and immunohistochemical methods. Pathologic damages observed in the mice caused by 3 different isolates were different from each other and the previous reports. It maybe due to the genetic difference of the pathogens. The pathogenic mechanism needs further study.